Hydraulic pump or motor



HYDRAULIC PUMP OR MOTOR Filed March 22, 1956 [Hi V FlG. 4

INVENTOR.

ROBERT W. BRUNDAGF.

ATTORNEY United States Patent G 2,925,044 HYDRAULICQPUMP R MOTOR Robert W. Brundage, Euclid, Ohio Application March 22, 1956, Serial No. 573,292

6 Claims. Cl. 103-120 This: invention pertains to the art of hydraulic pumps or motors and, more particularly, to a rotary positive displacement hydraulic pump or motor of the type having constantly increasing and decreasing volume chambers which are commutated by lands from inlet to outlet manifolds and vice versa.

[The invention is particularly applicable to internalgear type rotary pumps or motors and will be described as applied thereto although it will be appreciated that the inventionis equally applicable to, without limitation, vane or barrel type pumps or motors.

Rositive displacement rotary pumps are normally comprised ofinner and outer membersrelatively rotatable and so arranged as to define a plurality of chambers which progressively increase and decrease in volume to thus receive and discharge a hydraulic fluid. These chambers communicate with and are commutated between inlet and outlet manifolds by lands which also divide the manifold. i

The width of these lands relative to the width of the passages communicating the chambers with the manifolds in the direction of movement heretofore has been a very important part of pump design and operation.

Thus, if the width of the land is narrower than the.

width of the passage, then for an instant in the arc of rotation of the passage past the land, fluid can leak from the outlet manifold to the inlet manifold around the land through the passage. With high pressure pumps, substantial amounts of fluid can leak past the land in such event. This is ordinarily called leakage.

If the land, is Wider than the passage and, for example, the land is positioned adjacent a point in the movement of the chambers where they are decreasing volume, it will be appreciated that for an instant in the arc of rotation no fluid can leave the chamber and very high pressures within the chamber can result. This is ordinarily termed trapping and is considered very detrimental in pumps of the type to which this invention pertains. Trapping is the principal problem with which the present invention deals.

If the land is wider than the passage and is adjacent a point in the arc of movement of the chambers where their volume is increasing, there is an instant when fluid cannot enter the chamber and a vacuum results. A vacuum produces only relatively small pressure differentials, from that which ordinarily exist and is not considered particularlydetrimental.

Because of the problems of trapping and vacuum, it has ,,heretofore been conventional to position the lands opposite the point of minimum and maximum volume where the problems of trapping and vacuum are minimized. Here ,the rate of volume change per arc of rotation isrelatively low. Also, with the land positioned adjacent the point of maximum volume, there is a vacuum created in the chamber as it approaches the point which. offsets the trapping which would occur after the chamber volume goesfrom increasing to decreasing,

However, in substantially all pumps of the type to "ice which this invention pertains there is a problem of leakage between the individual chambers, one exposed to a high pressure and the other to a low pressure, between the surfaces which separate the two chambers. It has been considered desirable to increase the width of a land, either positioned adjacent the points of minimum and maximum volume or otherwise in the pump, so that the land will cover a span of two or more chambers. In such a case, however, the problem of trapping becomes very serious.

This problem of trapping also exists in a serious way where the lands are of a width to prevent leakage and are moved from the points of minimum and maximum volume so as to adjust the volume of fluid passing through the pump or motor fora given are or rotation or per unit movement.

One method and arrangement for preventing some of the difliculties referred to above has been described in my co-pending patent application Serial No. 497,779 filed March 29, 1955, now Patent No. 2,898,862, issued March 29, 1-959. In this application, an arrangement is described wherein only the land normally located adjacent the point of minimum chamber volume is adjustable in the direction of rotation; that is, in the direction of increasing volume. The other land; namely, the one adjacent the point of maximum volume of the chambers, remains fixed. With such an arrangement, some of the fluid underpressurein the outlet manifold flows into some of the increasing volume chambers. These increasing volume chambers then act as a motor to recover the energy of the fluid or at least part of it.

Another method and arrangement for preventing these diificulties has been described in my co-pending application Serial No. 548,022 filed November 21, 1955. In this application, the arrangement is such that the decreasing volume chambers communicate during a portion of the time when opposite a land with an auxiliary passage which has either previously been in communication with an increasing volume chamber or is, at that time, in communication with such an increasing volume chamber and the increasing volume chamber is increasing its volume at a rate equal to, or greater than, the rate of decrease of the decreasing volume chamber.

The present invention contemplates a rotary pump or motor of the positive displacement type .wherein the lands may be of any relative width relative to the passages communicating the chambers with the manifolds Which is eflicient, which avoids the problems of trapping and leakage and which is simple in construction.

The present invention pertains to a variable volume, positive displacement hydraulic pump which is comprised of a plurality of members movable relatively to each other and defining a plurality of pumping chambers which revolve in a fixed closed path of movement, the chambers graduallyincreasing in volume after they pass a fixed point of minimum volume along this path of movement until they reach a fixed point of maximum volume along this path and then gradually decreasing in volume until they again reach the minimum volume point, means defining an arcuate inlet manifold and an arcuate outlet manifold including a pair of lands, one at each arcuate end of the manifolds and sealingly separating the manifolds from each other, the manifolds and lands being disposed circumferentially along the path of movement of the chambers, and an opening for each chamber which revolves therewith, each of the chamber openings moving past the lands to alternately communicate its associated chamber with either the inlet manifold or the outlet manifold. One of the lands is normally located at the point of maximum volume, so that as each chamber reaches and passes through maximum volume its,

opening shifts from communication with the inlet maul fold to the outlet manifold. The other land is adjustable along the" path of movement of the chambers so as to change the point in that path at which each opening moves past such land and shifts communication of its chamber from the outlet manifold to the inlet manifold, therebyenabling the output volume of the pump to be varied; This other land has a circumferential width greater than the circumferential width of each opening, so that when adjusted so as to beo'pposite a decreasing volume chamber, it will prevent leakage and will normally tend to cause trapping.

However, and inaccordance with the present invention, this other land includes valve means arranged to happened by pressure in such decreasing volume chamher, when such chamber is closed by this land, in excess of that in the outlet manifold so as to communicate such jchamhjer with the inlet manifold at this time and er b avo d tr p n Still further in accordance with the invention, at least the land to be positioned opposite the decreasing volume chambers 'includesa movable member biased to closed position by pressures i'n the outlet manifold and moved by excess pressurein the decreasing volume chamber opposite the land to communicate the chamber discharge passage with the inlet manifold.

Further accordance with the invention, at least the land to be positioned opposite the decreasing volume chambegs includes an exp'ansible chamber biased to a minimum volume by pressures in the outlet manifold and arranged to communicate with the chamber discharge passage and expand when pressure in the decreasirlg volume chamber exceeds that of the pressure in the outlet manifold.

Still further in accordance with the invention, the

movable member may be formed of a rigid material yieldingly biased by spring pressure or may be formed of a material having a low modulus of elasticity capable of deflecting under the pressures in the pump or motor.

Either one, or both, lands may be adjustable relative to the point of minimum and maximum volume of the mb sr The principal object of the invention is the provision of anew and improved hydraulic pump or motor of the type where the increasing and decreasing volume chambers are commutate d from one manifold to another by lands whereintra'pping pressures are immediately relieved by communicating the decreasing volume chamberto the inlet manifold. I I

Another object of the invention is the provision of a'new and improved hydraulic pump or motor of the type described, having lands which are of a width to prevent leakage but which pump or motor is not subject to the problems of trapping.

Another object of the invention is the provision of a new and improved hydraulic pump or motor which is simple in construction, positive in operation and has a high efficiency without troubles from trapping.

Another object of the invention is the provision of a new and improved rnean's of leading off trapping pressures in a hydraulic pump or motor.

Theinvention may take physical form in certain parts of arrangements of parts, all differing radically in appearance one from the other, preferred embodiments of which will be described in detail 'in this -specification and illustrated in the accompanying drawing which is a part hereof and wherein: V

Figure 1 is a side cross-sectional view taken approximately in line '1--1 of Figure 2 of an internal gear-type pump "ormotor'embodying'the present invention;

Figurelis across-sectional view of Figure 1 taken approximately'in the'linelfi thereof; 7

Figure'3 is afragmentary' detail view showing an alternative' embodiment of'the invention;

Figure "4is "a' crass-seesaw view of Figure 3 taken approximately'in the line thereof; and,

Figure 5 is a view similar to Figure 3 but showing a still further alternative embodiment of the invention.

Referring now to the drawings wherein the showings are for the purposes of illustrating preferred embodiments of the invention only, and not for the purposes of limiting same, Figures 1 and 2 show a plurality of, in this case 2, members 10, 11 relatively movable to each other and so formed as to define a plurality of chambers 12, 13 which respectively increase and decrease in volume as the chambers move. The reference character 12 indicates those chambers which are increasing in volume and the reference character 13 indicates those .which are decreasing in volume.

The members l0, 11 can be either the relatively movable members of a vane type pump, the movable members of a reciprocating rotatable cylinder or wobbleplatetype pump, or any other form of pump wherein there are a plurality of chambers which progressively increase and decrease in volume as the members move, and positive chambers are, continuously in communication wilt the input manifold and another part are continuously in cornmunication with an output manifold. v

In the embodiment of the invention shown, an internal gear type pump is employed wherein the inner "gear is the member and the outer gear is the member 11 and these two gears rotate relative to each other .Withthe direction of rotation being assumed, for the purpose of describing the invention, as clockwise,

The inner gear 10 has a plurality of teeth 15, and intermediate roots 16 which mesh with teeth 17 and roots 18 of the outer gear 11. There is one less tooth "on the inner gear. 10 than there is on the outer gear 11, and

the shape of the teeth and roots is soarran'gedthat at all times each tooth 15 will have a point 19 of sealing en}.

gagement with the tooth 17 of the outer gear 101 .Ohviously, there could be greater than one tooth differential.

The axes of rotation of the two gears 10, '11 are ofiset one from theother and in the embodiments shown, there is a point it of minimum volume and a point x of maximum volume of the chambers '12 and 13. It will be noted that a line through the points n, x divides the chambers 12 and the chambers 13 from each other. 0bviously, when the chambers are exactly opposite either the point n or x, there is no relative increase or decrease of volume although just prior to and after passing by these two points there is a slight' change o f'volume.

The inner gear 10 is mounted for rotation on 'a drive shaft and is keyed thereto by means ofa key 26.

The two gears 10, 11 are of the same axial thickness and are mounted for rotation in a housing 28 having a circular cavity 30 of a diameter somewhat greater than the outer diameter of the gear 11 and an outer'peripheral surface 31 concentric with the outer-surface 32 of the gear 11.

A control member 35 in the form of a circularplate and having a diameter generally equal to the-diameter'of the cavity 30 is disposed at the base thereof and with the gears 10, 11 substantially fills the cavity 30. Acover plate 36 fits over the cavity 30 and is in sealing-arrangement with the right-handside of the gears 10, 11 "as viewed in Figure 1, as is the control member 35 which is in sealing arrangement with the left-hand side of the gears 10, 11 as viewed in Figure -l.

The control member 35 has'a land-indicated enerally at 37, which extends axially into the'space between the surfaces 31, 32 and is in sliding butsealing'eng'agenient with the surfaces. Additionally, there is a land 38' -fixed:

ly positioned at the point x and in 'sliding, sealing em' gagement w'ith'the surface 32. Theselands :37, 38 divide the space between the surfaces 31, 32 into an inlet' manifold'40 and an outlet manifold 41. Pip'es 42,43 communicate through the wall of the housing 28 -with the inlet and outlet manifold'40, 41' respectively to prm vide an inlet "and-outlet passage for the pump. It will be noted that" the pipes" 42, '43 areloeate'dabout 15 P the direction of rotation from the points of minimum and maximum volume "n, x. Obviously, the pipes 42, 43 could be otherwise located butbecause of the adjustability of the land 37, this location of the inlet and outlet point is particularly advantageous to give maximum range of adjustability with a maximum degree of eflicicncy. While the land 38 is preferably fixably positioned, it can be made adjustable along with the land 37 by fastening it to the control plate 35.

The control member 35 is rotatably supported in the housing 28 and has a boss 45 extending into a counter bore in the housing 28. The boss 45 has helical teeth 46 formed in its surface engaged by a worm wheel 47 having a shaft not shown which extends through the side of the housing 28 and is accessible from the outside so that the control member 35 may be fixedly adjusted to any desired point.

It will be noted that the shaft 25 extends into a recess in the right-hand face of the control member 35 for the purpose of providing a physically strong rotatable assembly.

Each chamber 12, 13 has a passage 50 extending radially outwardly from each root 18 through the outer surface 32 of the gear 11 communicating either with the inlet manifold 40 or the outlet manifold 41 as the gears rotate.

In operation, as the gears 10, 11 rotate, the chambers 13 constantly increase in volume thus creating a suction effect. Hydraulic fluid, not shown, flows inwardly through the pipe 42 to the inlet manifold 40, then through the passages 50 to the chambers 13.

Hydraulic fluid also flows out ofthe decreasing volume chambers 12 through the passages 50 into the outlet manifold 41 and then through the pipe 43. The lands 37, 38 prevent communicationbetween the inlet and outlet manifolds 40, 41. In effect, the passages are commutated as they pass the lands. i

If the stops 37,38 are positioned adjacent the points of minimum and maximum volume n, x respectively, the pump would pump its maximum capacity. Thus, all of the enlarging chambers 13 would be in communication through the passages 50 with the inlet chamber 40 and all of the decreasing volume chambers 12 would be in communication with the outletmanifold 41.

In accordance with the present invention, however, the land 37 is adjustable away from the point n to provide an adjustable output volume for the pump for a given constant rotational speed. Thus, if the land 37 is adjusted to the position shown in Figure 2, it will be seen that the outlet manifold 41 is in communication with only a portion of the decreasing volume chambers 12 while the inlet manifold 40 is in communication not only with all of the increasing volume chambers 13, but with'the decreasing volume chambers 12 between the land 37and the point n. Thus the volume output of the pump is decreased.

It will be noted that the passages 50 each have a width a in the direction of movement. The relationship of the widthof the lands 37 in relation to the dimension a form an important part of the present invention. It should be noted that if the width of the land 37 is equal to or greater than the dimension a, then for a fraction of the arc of rotation, fluid cannot be discharged nor taken into the passage 50. In the case where discharge of fluid is prevented, a situation, as previously referred to, called trapping arises wherein extremely high pressures internally of the decreasing volume chamber 13 can result.

On the other hand, if the width of the land 37 is made less than the dimension a then fora small fraction of the arc of rotation fluid can fiow from the outlet manifold around the land through the outer portions of the passage 50 to the inlet manifold 40. Leakage results. The present invention deals directly with this problem.

Thus, the land 37 is actually comprised of a plurality of minor, or auxiliary, lands, one of which is operable or movable to communicate the passage 50 with the inlet" manifold 40 when the pressures in the decreasing volume chambers opposite the land reach values above that in the outlet manifold 41.

As shown in Figure 2, the land 37 is actually comprised of a fixed land 37b of a width b less than the passage width a and a movable land 370 of a. width 0 greater than the width a of the passage 50. The lands 37b and 370 face or are exposed to the outlet and inlet manifolds respectively. The land 370 is preferably movably supported relative to the land 37b and is held in position by an L-shaped member 37a spaced from the land 37b and terminating short of the outer surface 32 of the gear 11 to form a passage 55. It will be noted that if the auxiliary land 37c is moved away from the surface 32, the passages 50 can communicate with the inlet manifold 40.

The auxiliary land 37c preferably has projections 53 on the outer surface thereof, spacing the outer surface of the land 370 from the inner surface of the circumferentially extending portion of the member 37a. Additionally, the. outer surface of the land 37b is spaced from this inner surface to provide a passage 54 from the outlet manifold 41 to the outer surface of the auxiliary land 37c. Thus, the land 37c is continuously urged into engagement with the surface 32 by the pressures in the outlet manifold 41.

In accor'dancewith the invention, the land 37b is preferably formed of a material having a high modulus of elasticity such as steel, metal or rigid plastic. However,

nicate the passage 50 with the inlet manifold 40 through a passage 55.

In operation, thepressure in the outlet manifold 41 continuously presses theland 37c toward the surface 32 to maintain the passages 50 closed while opposite the land 37. However, if for any reason the pressures in the chambers 12 should reach a value above that of the pressure in the outlet manifold'41, it will be appreciated that the land 37c will be deflected and raised from the surface 32 to allow pressure to flow through the passages 50 and 55 to the inletmanifold 40.

i In effect, there is provided a differential pressure valve acting to relieve pressure in the decreasing volume chambers when pressures therein tend to exceedpressures in the outlet manifold.

Figures 3 and 4 show an alternative embodiment of the invention. Here the adjustable land indicated generally at 67 is comprised of a fixed land 67b of rigid material and a pair of movable lands 67c and 67d of a flexible material and arranged so as to move relative to the fixed land 67b as will appear.

The land 67b is preferably of metal either integral or fastened to the control member 35 and has a surface in sealing engagement with the outer surface 32 of the gear 11 and a width B less than the dimension a. The movable lands 67c, 67d are actually the legs 68c, 68d of a U-shaped member 68 formed of a material having a low modulus of elasticity such as nylon, rubber or the like and having a base 68a in sliding sealing engagement with the surface 31. The legs 68c, 68d extend in spaced relationship on both sides of the land 67b to form spaces 69c, 69d respectively on both sides of the land 67b. The ends of these legs 68c, 68d sealingly and slidingly engage the surface 32. The lands 67c, 67d have a width when combined with that of the width of the lands 67b greater than that of the width a of the passage 50.

In operation, the pressure in the outlet manifold 41 tends to bias the leg 68c against the side of the land 67b. Thus, as the passage 50 moves past the land 67, trapping would normally tend to occur. However, when pressure in the passage 50 exceeds the pressure in the outlet manifold 41, the legs 680 will move toward the outlet manifold 41 and the trapped fluid can flow into the space 7 69, If the space 69s is not sufficient to relieve the trapping pressure, the leg 68%; can continue to move until the fiuid can flow directly into theoutlet manifold 41.

As the passage 50 continues to move past the land 67, the trapped fluid can then flow into the space 69d and if this space is not sufficiently large, then the leg 680. can be further deflected in the direction of the inlet manifold 41 until a passage is provided between the passage 50 and the inlet manifold 40.

It will be appreciated that the land 67c, 67d could be comprised of rigid members yieldingly biased toward the surface 32 as will generally be described in connection with Figure '5.

Thus, Figure shows a stillfur-theralternative embodi ment of the invention constructed in a manner quite sim ar to, that of Figure 2 but with the exceptionthat the land 71! -is forniedofia material having a high modulus ofelasticityand arranged so as to be biased to he ssal en a m n w h hi s fa e 2. by means of a spring 71 between theportion'37a and the upper or outer surface of the member 70'. In ,a like manner, the upper surface of the ,member 70, isexposed to the pressures in the inlet chamber41. Thus, whenever the pressure in the passage '50 exceeds the pressure in the outlet manifold 41 plus the force of thespring 71, the member 70 will move radially outwardly to communicate the passageSt) with the inletmaniiold and thus bypass away theiiluids which would be trapped.

It will thus beappreciated that embodiments .of the in-. vention have been described wherein the land to be positioned opposite thedischarge or decreasing volume chambers has means for. receiving and/or bleeding-tolfltrapped fluid to the inlet; chamber byrneans of a member movable under the effects of the trapped pressure to create the necessary space or fiuid passage. Obviously, by so adjusting ,the rnodulus of elasticity of the low-modulus material or the. bias of the .springjl, the pressure ,at which such valving occurs can be adjusted from either a pressure just slightly greater than the ,pressure in the outlet manifold to pressures substantially greater.

7 Having thus described my invention, I claim:

1, In a variable volume-hydraulic pump comprised of a plurality of members movablerelatively to each other and defining a plurality of pumping chambers revolving in a fixed, closed path-of movement, said chambers gradi y c eas n in me a rlh ss xe ,iw of minimum volume on said path of movement until e reach a fix an nt 29 m x mum vo um vsaid pa h of m en and then ra u ly r s n n volume until they reach .said fixed point of :minimum volume, means defining-an arcuate inlet and an arcuate outlet manifold including a pair .of lands one at each arcuate end of said manifolds and sealingly separating said manifolds one from theother, said manifolds and lands being disposed circumferentially along said path of movement ofthe chambers, an'opening for each chamber revolving therewith, each of said openings moving past said lands to alternately communicate its associated chamber with either said inlet-orsaid outlet manifold, one of saidlands @being normallydocated at thepoint tat-maximum vqlurneso th t as eac ha be ea s and passes thtough ma mum volume its opening shifts fromcommunication with the inlet manifold to the outlet manifold, said other land being adjustable along the p f movement of said chambers so s t c ng he point in the path of movement at which each opening moves past said other land and shifts communication of its chamber from the outlet to the inlet manifold whereby the output volume of saidpump may be varied, the improvement which comprises said other land having a circumferential width greater than the circumferential width of each opening, such that when adjusted so as to be opposite a decreasing volume chamber it will prevent lea ag an n rma y tendt ca se ppin S d other land' including valve means opened by pressure.

in said decreasing volume chamber when closedby said other land'in"eXcess of that in the outlet manifold for" communicating said decreasing volume chamber withsaid inletrmanifold'." r

2. The pump of claim 1 wherein said other land has a first portion 'of a circumferential width less than the circumferential width of each opening, and a second portion of accircumferential width such that the total circumferential width of said'first and second portions is greater than the circumferentiabwidth of each opening,

said' second portion being movable under the influence of pressure in an opening when gpposite said other land to communicate said opening with the inlet manifold.

3. Ihe pump totclaim 2 wherein said second portion has a modulus of elasticity substantially lower than said first portion. i

4. The pump of claim 2 wherein. said second portion has a modulus of elasticity substantially lower than said first portion and is urged by pressurei in the outlet manifold to aposition .blockingcoinmunication of said opening with the inlet manifold.

5. The pump of' claim 2 wherein there is provided spring means biasing said second portion to .a position blocking communication of said opening with the inlet manifold.

6 The pump of claim 5 wherein said second portion is also urged to ,saidblocking position by pressurein the outlet manifold. l

References Cited inthe file of this patent UNITED STATES PATENTS 1,482,807 Newberg Feb. 5, 1924 1,964,330 Pitt June 26, 1934 1,970,146 Hill Aug. 14, 1934 2,053,919 Pigott 7.7. Sept. 8, 1936 2,192,660 Johnson Mar. 5, 1940 2,426,491 Dillon Aug. 26, 1947 2,599,321 Topanelian May 30, 1950 2,606,503 Shaw Aug 12, 1952 2,618,224 Haugdahl Nov. 18, 1 952 2,630,759 MahlOn Mar. 10, 1953 2,658,344 Welch Nov. 10, 1953 2,685,255 Carner Aug. 3, 1954 2,749,843

Nu ing une 2, 6 

